GeForce GT 640 DDR3 vs GeForce GTX 460 1GB

Intro

Compare that to the GeForce GTX 460 1GB, which features GPU core speed of 675 MHz, and 1024 MB of GDDR5 memory running at 900 MHz through a 256-bit bus. It also is made up of 336 SPUs, 56 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 460 1GB		160 Watts
	Difference: 95 Watts (146%)

Memory Bandwidth

In theory, the GeForce GTX 460 1GB will be 102% faster than the GeForce GT 640 DDR3 overall, due to its greater bandwidth. (explain)

GeForce GTX 460 1GB		115200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 58176 (102%)

Texel Rate

The GeForce GTX 460 1GB will be quite a bit (more or less 31%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 460 1GB		37800 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 9000 (31%)

Pixel Rate

The GeForce GTX 460 1GB should be quite a bit (approximately 50%) faster with regards to full screen anti-aliasing than the GeForce GT 640 DDR3, and also should be able to handle higher screen resolutions while still performing well. (explain)

GeForce GTX 460 1GB		21600 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 7200 (50%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the maximum amount of data (counted in MB per second) that can be transported past the external memory interface within a second. The number is calculated by multiplying the bus width by the speed of its memory. In the case of DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total number of texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly record to its local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.